inl.go

Documentation: cmd/internal/obj

     1  // Copyright 2017 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  package obj
     6  
     7  import "cmd/internal/src"
     8  
     9  // InlTree is a collection of inlined calls. The Parent field of an
    10  // InlinedCall is the index of another InlinedCall in InlTree.
    11  //
    12  // The compiler maintains a global inlining tree and adds a node to it
    13  // every time a function is inlined. For example, suppose f() calls g()
    14  // and g has two calls to h(), and that f, g, and h are inlineable:
    15  //
    16  //  1 func main() {
    17  //  2     f()
    18  //  3 }
    19  //  4 func f() {
    20  //  5     g()
    21  //  6 }
    22  //  7 func g() {
    23  //  8     h()
    24  //  9     h()
    25  // 10 }
    26  // 11 func h() {
    27  // 12     println("H")
    28  // 13 }
    29  //
    30  // Assuming the global tree starts empty, inlining will produce the
    31  // following tree:
    32  //
    33  //   []InlinedCall{
    34  //     {Parent: -1, Func: "f", Pos: <line 2>},
    35  //     {Parent:  0, Func: "g", Pos: <line 5>},
    36  //     {Parent:  1, Func: "h", Pos: <line 8>},
    37  //     {Parent:  1, Func: "h", Pos: <line 9>},
    38  //   }
    39  //
    40  // The nodes of h inlined into main will have inlining indexes 2 and 3.
    41  //
    42  // Eventually, the compiler extracts a per-function inlining tree from
    43  // the global inlining tree (see pcln.go).
    44  type InlTree struct {
    45  	nodes []InlinedCall
    46  }
    47  
    48  // InlinedCall is a node in an InlTree.
    49  type InlinedCall struct {
    50  	Parent   int      // index of the parent in the InlTree or < 0 if outermost call
    51  	Pos      src.XPos // position of the inlined call
    52  	Func     *LSym    // function that was inlined
    53  	ParentPC int32    // PC of instruction just before inlined body. Only valid in local trees.
    54  }
    55  
    56  // Add adds a new call to the tree, returning its index.
    57  func (tree *InlTree) Add(parent int, pos src.XPos, func_ *LSym) int {
    58  	r := len(tree.nodes)
    59  	call := InlinedCall{
    60  		Parent: parent,
    61  		Pos:    pos,
    62  		Func:   func_,
    63  	}
    64  	tree.nodes = append(tree.nodes, call)
    65  	return r
    66  }
    67  
    68  func (tree *InlTree) Parent(inlIndex int) int {
    69  	return tree.nodes[inlIndex].Parent
    70  }
    71  
    72  func (tree *InlTree) InlinedFunction(inlIndex int) *LSym {
    73  	return tree.nodes[inlIndex].Func
    74  }
    75  
    76  func (tree *InlTree) CallPos(inlIndex int) src.XPos {
    77  	return tree.nodes[inlIndex].Pos
    78  }
    79  
    80  func (tree *InlTree) setParentPC(inlIndex int, pc int32) {
    81  	tree.nodes[inlIndex].ParentPC = pc
    82  }
    83  
    84  // OutermostPos returns the outermost position corresponding to xpos,
    85  // which is where xpos was ultimately inlined to. In the example for
    86  // InlTree, main() contains inlined AST nodes from h(), but the
    87  // outermost position for those nodes is line 2.
    88  func (ctxt *Link) OutermostPos(xpos src.XPos) src.Pos {
    89  	pos := ctxt.InnermostPos(xpos)
    90  
    91  	outerxpos := xpos
    92  	for ix := pos.Base().InliningIndex(); ix >= 0; {
    93  		call := ctxt.InlTree.nodes[ix]
    94  		ix = call.Parent
    95  		outerxpos = call.Pos
    96  	}
    97  	return ctxt.PosTable.Pos(outerxpos)
    98  }
    99  
   100  // InnermostPos returns the innermost position corresponding to xpos,
   101  // that is, the code that is inlined and that inlines nothing else.
   102  // In the example for InlTree above, the code for println within h
   103  // would have an innermost position with line number 12, whether
   104  // h was not inlined, inlined into g, g-then-f, or g-then-f-then-main.
   105  // This corresponds to what someone debugging main, f, g, or h might
   106  // expect to see while single-stepping.
   107  func (ctxt *Link) InnermostPos(xpos src.XPos) src.Pos {
   108  	return ctxt.PosTable.Pos(xpos)
   109  }
   110  
   111  // AllPos returns a slice of the positions inlined at xpos, from
   112  // innermost (index zero) to outermost.  To avoid gratuitous allocation
   113  // the result is passed in and extended if necessary.
   114  func (ctxt *Link) AllPos(xpos src.XPos, result []src.Pos) []src.Pos {
   115  	pos := ctxt.InnermostPos(xpos)
   116  	result = result[:0]
   117  	result = append(result, ctxt.PosTable.Pos(xpos))
   118  	for ix := pos.Base().InliningIndex(); ix >= 0; {
   119  		call := ctxt.InlTree.nodes[ix]
   120  		ix = call.Parent
   121  		result = append(result, ctxt.PosTable.Pos(call.Pos))
   122  	}
   123  	return result
   124  }
   125  
   126  func dumpInlTree(ctxt *Link, tree InlTree) {
   127  	for i, call := range tree.nodes {
   128  		pos := ctxt.PosTable.Pos(call.Pos)
   129  		ctxt.Logf("%0d | %0d | %s (%s) pc=%d\n", i, call.Parent, call.Func, pos, call.ParentPC)
   130  	}
   131  }
   132
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